398 The Rev. B. Powell on some Experiments 



exactly to an ioimense Leyden battery : the glass of the jars 

 represents the gutta percha; the internal coating is the surface 

 of the copper wire ; the external surface is the moistened earth. 

 To form an idea of the capacity of this new kind of battery, we 

 have only to remember that the surface of the wire is equal to 

 7 square metres per kilometre. Making such a wire communicate 

 by one of its ends with a pile, of which the other extremity is in 

 contact with the earth, whilst the other extremity of the wire is 

 insulated, must cause the wire to take a charge, of the same 

 character and tension as that of the pole of the pile touched by 

 it : — that is what came to pass in the first of the instantaneous 

 currents described. In Volta's experiment, on breaking the 

 communication between the pole and the battery and connecting 

 the two coatings of the latter by a conductor, an ordinary dis- 

 charge was obtained : — to this discharge correspond the two 

 instantaneous currents which are observed in opposite directions 

 at the two extremities of the charged wire, on communicating 

 their extremities with the earth, to the exclusion of the pile. It 

 will be understood, also, that the first instantaneous current, 

 namely, that which is connected with the charge of the wire, 

 ought to be equally produced, though of a lower intensity, even 

 when the other extremity of the wire is in communication with 

 the earth. The instantaneous current then precedes the conti- 

 nuous current, or, if the statement be preferred, is added to it at 

 the first moment. This instantaneous current has an intensity 

 much greater than that of the continuous current ; doubtless 

 because in the act of charging the wire, the electricity in going 

 to the different points of the wire passes through paths so much 

 the shorter as the points to be charged are nearer to the pile." 

 The above is from the Annates de Chimie, 1850, vol. xxix. 

 p. 398, &c. 



I am, Gentlemen, 



Your very faithful Servant, 



M. Faraday. 



LXIII. Note on some Experiments on Rotatory Motion. 

 By the Rev. Baden Powell, M.A., V.P.R.S. ^c. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



OBSERVING in a late Number some account of Professor 

 IMagnus's experiments, I conceive it may not be uninter- 

 esting to your readers to give the few following particulars rela- 

 tive to the closely-allied experiments of M. Fessel, and the dis- 

 cussions which have taken place respecting them, more especially 



